Welding of round tubular parts to each other is particularly difficult as at least one of the tubes must be cut in a compound, 3-dimensional curve in order to engage a second round tube for welding. For example, when welding two round tubes to each other, at least the secondary tube must have a saddle cut at its end which is to be joined to the outer wall of the primary tube. Where the saddle cut is not sufficiently precise, a gap is presented at the join position which is, at best, difficult to fill properly in order to make a sound, strong weld. A similar problem exists where a round tube must be welded to a flat surface at an angle, requiring a precise miter cut.
This problem is compounded by the fact that at the point of welding join of the two tubes, the primary tube will bend due to the stresses produced during welding. This bend not only results in the included join angle between the two tubes being incorrect, but also an unsightly bow is produced in the primary tube. Thus, taking for example a safety rail mounted on the deck of a boat adjacent the gunwale, the stanchions amid-ship are oriented normal to the horizontal railing and angled at the bow pulpit section and at the stern transom areas. In some cases the amount of warping of the horizontal rail occurring at every join of the stanchions is sufficient to present an objectionable wavy appearance.
The current practice of positioning of the parts with blocks in preparation for welding them together fails to provide any warp-compensation. The result is a slow process of repeated steps of partial welding followed by cooling so that the deformation is minimized. However, this process is inherently inaccurate due to the various sizes of tubing used. The result is experience-based guesswork that often results in do-overs and wasted material. Where the horizontal rail run is long, to have even only the last stanchion weld position warp, often results in rejecting the entire rail. This results in requiring remaking the entire rail, a substantial waste of time and material, and results in a substantial, two or three-fold increase of the rail assembly expense.
In addition, the welding of long rails having vertical and angular spindles that follow the contour of the gunwale is ordinarily a two or more person job, in that one person has to hold the rail and spindle members in proper angular position, and the other welds the rail to the spindle. This makes the assembly highly labor intensive; the work proceeds slowly, one spindle at a time.
Accordingly, there is an unmet need in the art for an improved round tubular work piece fixture system that compensates for welding-induced stress, accurately positions two (or more) tubes with respect to each other for welding, includes a way to accurately make saddle and miter cuts at the proper angle for joining the tubes, and permits setting up an entire rail assembly before welding to reduce labor costs, which fixture system is robust, simple to use, shortens construction time while reducing labor costs and reject fabrication loss.